ASTR178
Other Worlds
A/Prof. Orsola De Marco
9850 4241
orsola.demarco@mq.edu.au
Announcements
• Website of the book. It contains many articles and links:
http://bcs.whfreeman.com/universe9e/
Help questions (For this week)
• 1-28, page 232, 233.
• Most of the questions in this chapter are relevant
since I covered this chapter pretty thoroughly.
The Moon Practical
• All instructions have been posted on the website.
• Download the instructions and the sky chart.
• Go out at least 5 times between 14 August and 27
August ~8-9PM.
• Plot the Moon position on the Sky Chart provided, including
the Moon’s phase.
• Always go out at the same time for instance sometime
between 8 and 9 pm. IF YOU DO NOT THE EXPERIMENT
WILL NOT WORK.
• Answer the questions.
• Return the work to the boxes by September 17.
How to use a Sky Chart
In last class
• A quick wrap up of the magnetic fields in the Solar System.
• Earth’s energy sources
• The Greenhouse effect
• Earth’s inner layers (we started it, we will finish in this
class).
In this class
• Earth’s inner layers
• Plate tectonics
• A few rock definitions
• Earth’s early atmosphere and the rise of oxygen
• Earth’s current atmosphere, temperature, pressure and
circulation.
• The Human effect on the atmosphere and climate.
• We started talking about the moon, but this will be the
subject of Week 4, Class 1.
Richard Dixon Oldham
(Irish) 1858-1936
Hypothesized the existence of a molten core.
Inge Lehmann (Danish)
1888-1993
Hypothesized the existence
of the inner core
Alfred Wegener (German) 1880-1930
Plate tectonics
Arthur Holmes (British) 1890-1965
Roethosaurus – Early-mid Jurassic
From Queensland!
Tectonic activity is cyclic
• What we know of the tectonic movement
(Pangaea to today) lasted ~200 million years.
• Before then another cycle had taken place.
The supercontinent
before Pangaea was
named Rodenia (1100700 million years ago).
• Tectonic activity has
a ~500 million year
“cycle”.
“Pangaea Ultima” a possible next supercontinent
http://science.nasa.gov/science-news/
science-at-nasa/2000/ast06oct_1/
Types of tectonic activity
• Converging – subduction zones (Chile coast)
Himalayas
• Spreading – mid-Atlantic rift
• Sliding – St. Andreas fault
All plate boundaries are sources of
volcanism and earthquakes
Show Science Bulletins “Earthquakes today”: www.amnh.org/sciencebulletins/
Constructive and destructive plate boundaries
The St. Andreas Fault –
a type of conservative
plate boundary
A few “rock” terms
• Chemical elements make minerals (single atom or compounds)
• Single atom: diamond, gold nugget.
• Compound: feldspar=K,Al,Si,O; quartz=Si,O)
• One or more minerals make rocks
• Rock: granite = feldspar + quartz
Feldspar
Quartz
Granite
Plate tectonics and the variety of rocks
An example:
In the early Earth CO2 was outgassed
from volcanos. As it dissolved in the
oceans it formed carbonate minerals.
One such mineral, calcite became
part of sedimentary rocks such as
limestone, which were
later subducted, mixed up resulting in,
e.g., marble is a metamorphic rock.
Earth’s early atmosphere
• Early atmosphere: H, He, C, O, …. Same mix as the solar nebula
• H, He easily escape, some H forms H2O which remains
• Early atmosphere very dense and filled with water vapour
• Earth cools, vapour becomes liquid, forms oceans
• Earth would be very cold at this point, but CO2 outgassed from
volcanoes is a green-house gas and keeps Earth warmer than it
would be otherwise.
• CO2 is a green-house gas: in the atmosphere to keep the Earth
warm
• Some CO2 dissolves in water and goes in the oceans where it is
locked in rocks – some CO2 remains in the atmosphere
• When we release too much CO2 in the atmosphere we increase
the green-house effect and … the end of the story when we talk
more about the roasting surface of Venus!
The rise of Oxygen and complex life
• Photosynthesis + Respiration: regulation of O2
•
Life on Earth
Humans (~100,000 yr ago)
Cambrian explosion (~500 Myr ago)
Protoplanetary disk(~4.5 Gyr ago)
First life (~3.8 Gyr ago)
The rise of oxygen
• Science Bulletin’s piece
www.amnh.org/sciencebulletins/
Comparing Earth’s, Venus’ and
Mars’ atmospheres
Pressure decreases with altitude.
Temperature is more complicated …
At hundreds of
degrees, why is
the Shuttle not
burning up?
50% of the
atmosphere is
in the
troposphere.
The Earth biosphere
The Earth biosphere
• Climate can vary by natural causes (uneven Sun’s radiation, Earth’s axis
precession …).
• CO2 levels can also vary naturally (intense periods of volcanic activity:
extinction 250 million years ago driven by volcanoes in Siberia ….).
• However, human influence ha been far above these natural chances
(deforestation, destruction of the ozone layer, increase in CO2 emission).
90% of Ozone is between 40 and 60 km above ground.
Ozone is O3. It is broken down by UV light so it absorbs UV light and
protects us from it. It is then made by a reaction of O2 an O. It is also
destroyed by reacting with O, a reaction that is catalysed by other chemicals
such as CFCs
An Inconvenient Truth, by Al Gore
http://video.google.com/videoplay?docid=2078944470709189270
Observations of the Moon
• Aristotle thought that the lunar imperfections were
actually changes in density and the Moon was a perfect orb.
• Plutarch (46-120 AD) suggested that it was due to canyons
and valleys and might be inhabited.
• It was Galileo that finally put the matter to rest using
a telescope.
• Influence of the Moon on human life.
The Moon
One small step for (a) man,
one giant leap for mankind
http://www.youtube.com/watch?v=RMINSD7MmT4
Must watch the great Aussie movies “The Dish”.
Key Ideas
• The Earth’s Energy Sources: All activity in the Earth’s
atmosphere, oceans, and surface is powered by three sources
of energy.
• Solar energy is the energy source for the atmosphere. In the
greenhouse effect, some of this energy is trapped by infrared
absorbing gases in the atmosphere, raising the Earth’s surface
temperature.
• Tidal forces from the Moon and Sun help to power the motion
of the oceans.
• The internal heat of the Earth is the energy source for
geologic activity.
Key Ideas
• The Earth’s Interior: Studies of seismic waves (vibrations
produced by earthquakes) show that the Earth has a small,
solid inner core surrounded by a liquid outer core. The outer
core is surrounded by the dense mantle, which in turn is
surrounded by the thin low-density crust.
• Seismologists deduce the Earth’s interior structure by studying
how longitudinal P waves and transverse S waves travel
through the Earth’s interior.
• The Earth’s inner and outer cores are composed of almost
pure iron with some nickel mixed in. The mantle is composed
of iron rich minerals.
• Both temperature and pressure steadily increase with depth
inside the Earth.
Key Ideas
• Plate Tectonics: The Earth’s crust and a small part of its upper
mantle form a rigid layer called the lithosphere. The
lithosphere is divided into huge plates that move about over
the plastic layer called the asthenosphere in the upper
mantle.
• Plate tectonics, or movement of the plates, is driven by
convection within the asthenosphere. Molten material wells
up at oceanic rifts, producing seafloor spreading, and is
returned to the asthenosphere in subduction zones. As one
end of a plate is subducted back into the asthenosphere, it
helps to pull the rest of the plate along.
Key Ideas
• Plate tectonics is responsible for most of the major features of
the Earth’s surface, including mountain ranges, volcanoes, and
the shapes of the continents and oceans.
• Plate tectonics is involved in the formation of the three major
categories of rocks: igneous rocks (cooled from molten
material), sedimentary rocks (formed by the action of wind,
water, and ice), and metamorphic rocks (altered in the solid
state by extreme heat and pressure).
Key Ideas
• The Earth’s Magnetic Field and Magnetosphere: Electric currents in
the liquid outer core generate a magnetic field. This magnetic field
produces a magnetosphere that surrounds the Earth and blocks the
solar wind from hitting the atmosphere.
• A bow-shaped shock wave, where the supersonic solar wind is
abruptly slowed to subsonic speeds, marks the outer boundary of
the magnetosphere.
• Most of the particles of the solar wind are deflected around the
Earth by the magnetosphere.
• Some charged particles from the solar wind are trapped in two
huge, doughnut-shaped rings called the Van Allen belts. An excess of
these particles can initiate an auroral display.
Key Ideas
• The Earth’s Atmosphere: The Earth’s atmosphere differs from
those of the other terrestrial planets in its chemical
composition, circulation pattern, and temperature profile.
• The Earth’s atmosphere evolved from being mostly water
vapor to being rich in carbon dioxide. A strong greenhouse
effect kept the Earth warm enough for water to remain liquid
and to permit the evolution of life.
Key Ideas
• The appearance of photosynthetic living organisms led to our
present atmospheric composition, about four-fifths nitrogen
and one-fifth oxygen.
• The Earth’s atmosphere is divided into layers called the
troposphere, stratosphere, mesosphere, and thermosphere.
Ozone molecules in the stratosphere absorb ultraviolet light.
• Because of the Earth’s rapid rotation, the circulation in its
atmosphere is complex, with three circulation cells in each
hemisphere.
Key Ideas
• The Biosphere: Human activity is changing the Earth’s
biosphere, on which all living organisms depend.
• Industrial chemicals released into the atmosphere have
damaged the ozone layer in the stratosphere.
• Deforestation and the burning of fossil fuels are increasing the
greenhouse effect in our atmosphere and warming the planet.
This can lead to destructive changes in the climate.
Which of the following has the smallest effect on the
motions of the Earth's atmosphere and oceans?
A.
B.
C.
D.
E.
Q9.1
solar energy
the Earth’s internal heat
tidal forces
both B and C
This is a misleading question. All of these have
comparably large effects on the atmosphere and
oceans.
Which of the following has the smallest effect on the
motions of the Earth's atmosphere and oceans?
A.
B.
C.
D.
E.
A9.1
solar energy
the Earth’s internal heat
tidal forces
both B and C.
This is a misleading question. All of these have
comparably large effects on the atmosphere and
oceans.
What energy source creates clouds in our atmosphere?
A.
B.
C.
D.
E.
Q9.2
The Sun
Earth’s internal heat
Tidal interactions with the Moon
The solar wind
None of the above
What energy source creates clouds in our atmosphere?
A.
B.
C.
D.
E.
A9.2
The Sun
Earth’s internal heat
Tidal interactions with the Moon
The solar wind
None of the above
What energy source leads to mountain building on Earth?
A.
B.
C.
D.
E.
Q9.3
The Sun
Earth’s internal heat
Tidal interactions with the Moon
The solar wind
None of the above
What energy source leads to mountain building on Earth?
A.
B.
C.
D.
E.
A9.3
The Sun
Earth’s internal heat
Tidal interactions with the Moon
The solar wind
None of the above
In the greenhouse effect,
A. some infrared radiation emitted by the Earth’s
surface is absorbed by the atmosphere.
B. some ultraviolet radiation emitted by the Earth’s
surface is absorbed by the atmosphere.
C. vegetation traps thermal energy near the surface.
D. infrared radiation from the Sun is captured as it
enters the Earth’s atmosphere.
E. infrared radiation from the Sun is reflected by the
Earth’s atmosphere into space.
Q9.4
In the greenhouse effect,
A. some infrared radiation emitted by the Earth’s
surface is absorbed by the atmosphere.
B. some ultraviolet radiation emitted by the Earth’s
surface is absorbed by the atmosphere.
C. vegetation traps thermal energy near the surface.
D. infrared radiation from the Sun is captured as it
enters the Earth’s atmosphere.
E. infrared radiation from the Sun is reflected by the
Earth’s atmosphere into space.
A9.4
Which of the follow best describes the natural
greenhouse effect (not including human influence) on
Earth?
A. There is no natural greenhouse effect.
B. The natural greenhouse effect keeps Earth’s average
temperature relatively constant and above freezing.
C. The natural greenhouse effect has continuously
increased the average temperature of the
atmosphere and surface over the past 4.56 billion
years.
D. The natural greenhouse effect has continuously
decreased the average temperature of the
atmosphere and surface over the past 4.56 billion
years.
Q9.5
Which of the follow best describes the natural
greenhouse effect (not including human influence) on
Earth?
A. There is no natural greenhouse effect.
B. The natural greenhouse effect keeps Earth’s average
temperature relatively constant and above freezing.
C. The natural greenhouse effect has continuously
increased the average temperature of the
atmosphere and surface over the past 4.56 billion
years.
D. The natural greenhouse effect has continuously
decreased the average temperature of the
atmosphere and surface over the past 4.56 billion
years.
A9.5
Which of the following is not an important greenhouse
gas?
A.
B.
C.
D.
E.
Q9.6
Carbon dioxide
Methane
Water
Ammonia
All of these are important greenhouse gases.
Which of the following is not an important greenhouse
gas?
A.
B.
C.
D.
E.
A9.6
Carbon dioxide
Methane
Water
Ammonia
All of these are important greenhouse gases.
Which of the following is a correct statement about
seismic waves used to map the Earth’s interior structure?
A. P waves are longitudinal and are able to travel through
solids and liquids; S waves are transverse and can only
travel through liquids.
B. P waves are transverse and are able to travel through
solids and liquids; S waves are longitudinal and can only
travel through liquids.
C. P waves are transverse and are able to travel through
solids and liquids; S waves are longitudinal and can only
travel through solids.
D. P waves are longitudinal and are able to travel through
solids and liquids; S waves are transverse and can only
travel through solids.
Q9.7
Which of the following is a correct statement about
seismic waves used to map the Earth’s interior structure?
A. P waves are longitudinal and are able to travel through
solids and liquids; S waves are transverse and can only
travel through liquids.
B. P waves are transverse and are able to travel through
solids and liquids; S waves are longitudinal and can only
travel through liquids.
C. P waves are transverse and are able to travel through
solids and liquids; S waves are longitudinal and can only
travel through solids.
D. P waves are longitudinal and are able to travel through
solids and liquids; S waves are transverse and can only
travel through solids.
A9.7
The Earth’s magnetic field is generated by
A. electric currents in the liquid outer core; the field has
never changed direction.
B. electric currents in the liquid inner core; the field has
never changed direction.
C. electric currents in the liquid outer core; the field has
reversed many times in the past.
D. electric currents in the liquid inner core; the field has
reversed many times in the past.
E. electric currents caused by interactions with the solar
wind.
Q9.8
The Earth’s magnetic field is generated by
A. electric currents in the liquid outer core; the field has
never changed direction.
B. electric currents in the liquid inner core; the field has
never changed direction.
C. electric currents in the liquid outer core; the field has
reversed many times in the past.
D. electric currents in the liquid inner core; the field has
reversed many times in the past.
E. electric currents caused by interactions with the solar
wind.
A9.8
The Red Sea rift is
A. formed by two tectonic plates moving apart.
B. a subduction zone, where one plate is pushed under
the other.
C. a fold in the middle of a plate caused by compressing
forces on both sides of the plate.
D. a hot spot in Earth’s mantle, which is spreading two
plates apart.
E. the result of a earthquake that occurred thousands
of years ago.
Q9.9
The Red Sea rift is
A. formed by two tectonic plates moving apart.
B. a subduction zone, where one plate is pushed under
the other.
C. a fold in the middle of a plate caused by compressing
forces on both sides of the plate.
D. a hot spot in Earth’s mantle, which is spreading two
plates apart.
E. the result of a earthquake that occurred thousands
of years ago.
A9.9
The Mid-Atlantic Ridge is best described as
A. a line of undersea mountains caused by two plates
colliding and pushing each other upward.
B. a fold in the middle of a plate caused by compressing
forces on both sides of the plate.
C. a region where one plate is being subducted beneath
another.
D. a site where two plates are moving apart, allowing
molten subsurface rock to rise upward.
E. a region in the middle of a plate that happens to lie
over a hot spot in the mantle.
Q9.10
The Mid-Atlantic Ridge is best described as
A. a line of undersea mountains caused by two plates
colliding and pushing each other upward.
B. a fold in the middle of a plate caused by compressing
forces on both sides of the plate.
C. a region where one plate is being subducted beneath
another.
D. a site where two plates are moving apart, allowing
molten subsurface rock to rise upward.
E. a region in the middle of a plate that happens to lie
over a hot spot in the mantle.
A9.10
The Earth shows very little evidence of meteor impacts
because
A. plate tectonics is continuously recycling the Earth’s
crust.
B. wind and rain have continually eroded the Earth’s
surface.
C. very few meteors struck the Earth in the past.
D. vegetation has covered the craters.
E. Both A and B are correct.
Q9.11
The Earth shows very little evidence of meteor impacts
because
A. plate tectonics is continuously recycling the Earth’s
crust.
B. wind and rain have continually eroded the Earth’s
surface.
C. very few meteors struck the Earth in the past.
D. vegetation has covered the craters.
E. Both A and B are correct.
A9.11
If the early atmosphere of the Earth was composed of
carbon dioxide, why does the present atmosphere contain
oxygen molecules?
A. Volcanoes slowly enriched the Earth’s atmosphere
with oxygen.
B. When life first developed on the Earth, this life
produced oxygen from carbon dioxide by
photosynthesis.
C. Rainwater slowly broke down carbon dioxide into its
components.
D. Oxygen was captured from space over many millions
of years.
E. Solar radiation breaks down CO2.
Q9.12
If the early atmosphere of the Earth was composed of
carbon dioxide, why does the present atmosphere contain
oxygen molecules?
A. Volcanoes slowly enriched the Earth’s atmosphere
with oxygen.
B. When life first developed on the Earth, this life
produced oxygen from carbon dioxide by
photosynthesis.
C. Rainwater slowly broke down carbon dioxide into its
components.
D. Oxygen was captured from space over many millions
of years.
E. Solar radiation breaks down CO2.
A9.12
Ozone is a molecule made up of three oxygen atoms. The
ozone layer that protects the Earth’s surface from
ultraviolet light
A. has been present and stable for as long as we have
been measuring it.
B. has shown gradual changes over the last 20 years
with a hole appearing over Antarctica.
C. shows no holes yet but appears to be getting thinner.
D. shows rather large seasonal changes with large holes
appearing over the North and South Poles during
their respective winters.
E. is no longer present.
Q9.13
Ozone is a molecule made up of three oxygen atoms. The
ozone layer that protects the Earth’s surface from
ultraviolet light
A. has been present and stable for as long as we have
been measuring it.
B. has shown gradual changes over the last 20 years
with a hole appearing over Antarctica.
C. shows no holes yet but appears to be getting thinner.
D. shows rather large seasonal changes with large holes
appearing over the North and South Poles during
their respective winters.
E. is no longer present.
A9.13
The oxygen in our atmosphere is chemically reactive,
combining with other elements to form compounds, and
is also being used by respiratory life. Despite this, the
amount of oxygen in our atmosphere is not decreasing
because it is being replenished by
A.
B.
C.
D.
E.
Q9.14
outgassing from seawater.
volcanic eruptions.
biological activity, such as photosynthesis.
meteors and comets, which bring oxygen to the Earth.
solar radiation breaking down CO2.
The oxygen in our atmosphere is chemically reactive,
combining with other elements to form compounds, and
is also being used by respiratory life. Despite this, the
amount of oxygen in our atmosphere is not decreasing
because it is being replenished by
A.
B.
C.
D.
E.
A9.14
outgassing from seawater.
volcanic eruptions.
biological activity, such as photosynthesis.
meteors and comets, which bring oxygen to the Earth.
solar radiation breaking down CO2.